The present invention is concerned with a pressure vessel type of hydro-pneumatic accumulator which includes, for example, a thimble-shaped flexible bladder mounted in an outer shell, and which separates the interior of the shell into two chambers which are sealed from one another. The shell usually has a closed end. A port is formed in the closed end of the shell in communication with one of the two chambers within the shell. This port is usually referred to as the "liquid" port, and the adjacent chamber constitutes the "liquid" chamber of the accumulator. A cap is usually mounted on the other end of the shell, and it includes a valved "gas" port which communicates with the other chamber within the shell, and which constitutes the "gas" chamber.
A compressible gas, such as nitrogen, is permanently charged and compressed under high pressure, and is introduced through the gas valve into the gas chamber of the accumulator. Subsequently, an appropriate hydraulic liquid under high pressure is pumped through the liquid port into the liquid chamber.
As the hydraulic liquid is pumped into the liquid chamber, a balanced high pressure is maintained in both the liquid and gas chambers. By this action, energy is stored or absorbed by the gas chamber of the accumulator, which tends to force the hydraulic liquid out of the liquid chamber to enable the hydraulic liquid to perform useful work.
In the construction of accumulators of the type with which the present invention is concerned, and as explained above, the bladder is mounted within the shell between the gas valve at one end and the liquid port at the other end. As also mentioned above, in the usual prior art construction, one end of the shell is open, and a cap is usually welded to the shell to close the open end. This welding operation created problems in the prior art because the bladder was normally bonded to the shell prior to the welding operation, and the heat from the welding had a tendency to damage the bond and the bladder itself.
Attempts to overcome this problem in the prior art included the provision of an annular mounting sleeve which was bonded to the mouth of the bladder in coaxial relationship with the bladder, and which extended coaxially out from the mouth of the bladder. The opposite end of the sleeve was welded to the inner face of the cap, or to the shell, to mount the bladder in position within the shell. With such a construction, the only heat passed from the weld to the bladder bond was along the sleeve, and the sleeve was made sufficiently thin and sufficiently long so that any heat reaching the bladder bond was hopefully of insufficient intensity to damage the bond.
However, in order to perform its intended purpose, it was essential for the sleeve to support the bladder with its outer surface displaced radially inwardly from the inner surface of the shell, and although the construction was found to alleviate the problem of heat damage to the bladder bond, it was found that under pressure operating conditions a portion of the bladder adjacent the bond would "creep" up between the sleeve and the adjacent inner surface of the shell. This resulted in rapid wear and damage to the bladder.
In the construction of the present invention, an integral O-ring seal is provided between the mouth of the bladder and the inner end of the closure cap. The mouth of the bladder is resiliently drawn over the inner end of the closure cap to permit the integral sealing O-ring bead to be received in one of the grooves in the inner end of the retaining cap.
In accordance with the concepts of the invention, a separate integral anchoring bead is provided around the mouth of the bladder which is received in the second groove in the inner end of the closure cap or a separate retaining ring. The bladder is not bonded or in any way affixed to the closure cap, since the bladder is securely held on the closure cap without any need for bonding it to the cap, by the separate anchoring bead .